滤波器对偏振模色散的补偿

根据耦合非线性薛定谔方程 ,本文研究了偏振模色散如何影响各种码型的频谱 ,分析了滑频滤波器和固定滤波器对偏振模色散的补偿作用。研究结果表明 :偏振模色散对不同码型的频谱影响是不一样的 ,对色散管理孤子的频谱影响最大 ,产生新的频率分量也最多 ,而且每个新频率分量都较强 ,比入射频谱展宽许多 ;滑频滤波器和固定滤波器对偏振模色散都具有补偿作用 ,使最大可传输距离成倍增加 ,两种滤波器对偏振模色散的补偿作用相差较小 ;但是对色散管理孤子系统中的偏振模色散补偿效果最佳。     

偏分复用系统中偏振模色散补偿与偏分解复用一体化方案

本文建立了偏分复用系统中偏振模色散与信号偏振态变化引起信道串扰的数学模型, 分析了偏振模色散对偏分复用信道射频功率的影响, 并提出了适用于偏分复用系统的光域偏振模色散补偿与偏分解复用同时进行的方案: 用信道的射频功率作为反馈控制信号, 监测链路中偏振模色散和偏振态变化引起的信道串扰的大小, 用改进的粒子群优化算法对偏振控制器进行自适应控制, 同时完成偏振模色散补偿与偏分解复用. 在112 Gb/s偏分复用-差分正交相移键控(PDM-DQPSK)传输系统中仿真验证了该方案的有效性. 结果表明该方案可以使112 Gb/s-PDM-DQPSK传输系统完成自适应偏分解复用的同时, 在1 dB的光信噪比代价下, 使系统对偏振模色散的容忍度提高20 ps. 关键词： 偏分复用系统 信道串扰 偏振模色散 偏分解复用     

高双折射光子晶体光纤偏振模色散测量

对一种高双折射光子晶体光纤的偏振模色散进行了测量.实验用26 m长光子晶体光纤使皮秒光脉冲的两个正交偏振模产生了108 ps时延.运用脉冲时延法和固定分析仪法对这种高双折射光子晶体光纤的偏振模色散进行了实验测量，测量得到其偏振模色散参量可达4154 ps/km，对应的模式双折射度为1.25×10－3.这种新型的高双折射光纤可用于补偿光纤通信系统中的偏振模色散.     

快速数值差分递推算法在偏振模色散作用下光脉冲传输中的应用研究

利用快速数值差分递推算法对非线性薛定谔方程进行推导分析,得到一个同时考虑群速色散效应、非线性效应以及偏振模色散效应的时域快速数值差分递推关系,并将该方法应用于研究偏振模色散作用下的光脉冲传输,得到的计算结果分别与解析结果和传统的分步傅里叶算法所得结果进行对比,表明这种快速数值差分递推算法拥有很高的计算准确度,并且物理模型更加合理,完全适合分析计算偏振模色散作用下的光脉冲传输问题.利用该方法研究了光脉冲的畸变以及脉冲展宽问题,获得的计算结果为光纤传输系统的设计提供了参考.     

二阶偏振模色散对高速高斯光脉冲在单模光纤中传输的影响

研究二阶偏振模色散（PMD）对高斯光脉冲在单模光纤中传输产生的影响，给出输出光脉冲的时域表达式。分析表明，输出光脉冲在每个基本偏振态上仍保持高斯形状，但其频率啁啾及脉宽等特性都已改变，文中对这些变化与二阶偏振模色散之间的关系进行了讨论。通过比较10Gb/s和40Gb/s的光传输系统中二阶偏振模色散的影响，可以发现，若规定脉冲展宽不能超过脉宽的十分之一，40Gb/s系统所能容忍的二阶偏振模色散极限值比10Gb/s系统小一个数量级。     

光纤传输系统数值模拟中光纤节长度和步长的选取

随着光纤传输系统中传输速率逐渐提高,必须要考虑光纤传输系统中的偏振模色散。光纤传输模型用非线性薛定谔方程描述,利用分步傅立叶方法可计算光脉冲在光纤中的传输。分析了考虑偏振模色散时,不同光纤节长度和步长的选取对仿真结果的影响。     

偏振度作为反馈信号进行偏振模色散补偿的研究

对40Gb／s光纤通信中归零码和非归零码光脉冲的偏振度随二阶偏振模色散的变化规律进行了数值模拟,结果表明由于二阶偏振模色散的影响,偏振度的变化趋势呈现出震荡性,二阶偏振模色散对归零码的偏振度要比非归零码的偏振度影响明显;同时搭建了偏振模色散补偿系统,对系统进行数值模拟和实验所得到的结果都表明,以偏振度作为反馈信号,采用粒子群优化算法作搜索算法能够有效地对归零码和非归零码系统的一阶及高阶偏振模色散进行自适应补偿。     

双折射光纤中偏振复用技术的三阶色散抑制和补偿

针对三阶色散对零色散波长附近光脉冲偏振复用技术的破坏作用，提出了使用色散平坦光纤来抑制三阶色散的影响。然而用色散平坦光纤只能在脉冲短距离传输时有效，故提出用正负三阶色散交替的光纤补偿三阶色散对光脉冲偏振复用技术的影响。研究发现该补偿方案能有效地抵消线路的总三阶色散，实现了偏振脉冲长距离稳定传输。     

基于光信号偏振度的偏振模色散补偿系统的研究

偏振模色散已成为当前发展高速长距离光纤传输系统的主要限制因素。理论上分析了光纤一阶偏振膜色散效应对高速伪随机非归零码／归零码光信号偏振度的影响，并利用数值模拟的方法分析了信号不同输入偏振态以及高阶偏振膜色散效应对非归零码光信号偏振度的影响。最后对利用信号偏振度作为反馈控制信号的自适应偏振膜色散补偿系统的补偿性能进行了分析，大量统计分析结果表明对于10Gbit／s的非归零码光纤传输系统，当传输线路的平均偏振膜色散值小于43ps时，利用极大化输出信号偏振度的偏振膜色散补偿系统对信号眼图的补偿概率可以达到99．99％．     

超高偏振模色散光纤中光脉冲传输行为的研究

利用耦合非线性薛定谔方程分析了光脉冲在超高偏振模色散光纤中传输时，偏振模色散引起脉冲分裂。并用基模的两正交偏振分量耦合走离解释了脉冲分裂的成因。利用偏振模色散为237．95ps／km^1/2的光纤进行了实验验证。     

Jitter suppression by guiding filters in combination with dispersion management

Enhancement of jitter suppression of a soliton by combination of fixed-frequency filters with periodic dispersion compensation is predicted in an analytical form by means of the Fokker-Planck equation for the soliton's random walk. The result depends on the dispersion-compensation period but not on the ratio of the dispersions. Another result is presented that can help one to understand jitter suppression by dispersion compensation without filters, which was observed in recent experiments.     

Simulative analysis of soliton-based DPSK transmission system

The effectiveness of the conventional dispersion compensation techniques: DCF, FBG and OPC to use with soliton transmission is presented. The frequency shifts of solitons induced by collisions between different channels in a soliton WDM system can be reduced by dispersion compensation. The reduction mechanism applied is the cancellation of the shifts generated in both normal and anomalous dispersion regimes. It is analyzed that phase jitter can be reduced by the use of midway spectral inversion.     

Normalized LMS digital filter for chromatic dispersion equalization in 112-Gbit/s PDM-QPSK coherent optical transmission system

High bit rates optical communication systems pose the challenge of their tolerance to linear and non-linear fiber impairments. Coherent optical receivers using digital signal processing techniques can mitigate the fiber impairments in the optical transmission system, including the chromatic dispersion equalization with digital filters. In this paper, an adaptive finite impulse response filter employing normalized least mean square algorithm is developed for compensating the chromatic dispersion in a 112-Gbit/s polarization division multiplexed quadrature phase shift keying coherent communication system, which is established in the VPI simulation platform. The principle of the adaptive normalized least mean square algorithm for signal equalization is analyzed theoretically, and at the meanwhile, the taps number and the tap weights in the adaptive finite impulse response filter for compensating a certain fiber chromatic dispersion are also investigated by numerical simulation. The chromatic dispersion compensation performance of the adaptive filter is analyzed by evaluating the behavior of the bit-error-rate versus the optical signal-to-noise ratio, and the compensation results are also compared with other present digital filters.     

Analysis of a New Method of Dispersion-Supported Transmission for Dispersion Compensation

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色散补偿光纤通信系统中孤子之间的相互作用

采用变分原理与位力定理研究了非线性光通信系统色散补偿方案中,相邻孤子之间的相互作用对孤子传输特性的影响。结果表明:在相位匹配与等幅孤子注入时,在普通单模光纤中这两个孤子先相互吸引,而后又相互排斥,显现周期性碰撞的变化规律,形成束缚孤子态,而在色散补偿光纤中传输的孤子之间不发生碰撞;对相位不匹配与等幅孤子注入,孤子之间发生分离;对相位匹配和不等幅孤子注入,在色散补偿光纤中传输的孤子,如果初始间隔φ0越小,应注入较大的初始幅值差η0,以利于孤子的传输。     

一种基于Optisystem的静态与动态色散补偿相结合方案研究

介绍色散补偿光纤DCF及动态啁啾光纤光栅FBG的补偿技术并比较其优缺点,提出在传统光传输系统末端加入动态FBG的方案,通过Optisystem仿真软件搭建40 Gbit/s的光传输系统,用FBG仿真光传输400 km的Q值为3.745,误码率为7.419 42e-5,用DCF静态混合补偿和静态与动态相结合的补偿方案分别仿真并比较两种方案传输相同距离的Q值和误码率的大小,证明提出的静态加动态的方案提高了光传输性能。     

具有电色散补偿的10 Gb/s脉冲转换器的研制

设计并研制了带电色散补偿功能的10 Gb/s脉冲转换器。电色散补偿通过时域均衡的方法,消除光纤色散带来的码间串扰;将电色散补偿芯片纳入脉冲转换器设计中,从而提高了其传输距离。所研制的样品光发射部分采用分布反馈激光器加电吸收调制器集成光源,接收部分采用带互阻放大器的雪崩光电二极管光电探测器模块,电色散补偿芯片对光电探测器输出的码流执行色散补偿算法。对样品进行的测试结果表明该脉冲转换器背对背接收灵敏度为-24.6 dBm,经过100 km G.652光纤传输后接收灵敏度为-20.8 dBm。未加电色散补偿功能时,采用相同的光源传输距离仅为50 km。     

Effect of filters on solition collisions in WDM systems with lumped amplifiers and periodically varying dispersion

The effect of frequency-guiding filters on soliton collisions in wavelength-division multiplexing systems with lumped amplifiers and periodically varying dispersion has been investigated. The evolution equations for the soliton frequency shift and time shift are derived. The numerical results indicate that the filters make the frequency shift resulting from soliton collision tend toward zero; thus the system performance is improved considerably.     

Mitigation of phase noise in dispersion compensated quasi-linear optical transmission systems: Analysis

We theoretically investigate the phase noise in quasi-linear optical transmission systems and study the mitigation of phase noise by properly choosing periodic dispersion compensation and amplification. Variational method is used to deduce the analytical formula for calculating the phase fluctuations of a Gaussian pulse. The analytical predictions are then checked against direct simulations by numerically solving the nonlinear Schrödinger equation. We find that stronger dispersion compensation maps can be used to reduce phase noise and it can be further mitigated by modifying the dispersion map appropriately. It is also found that shorter amplifier spacing yields lower phase noise. We also explore the effect of pre-, post- and bi-end dispersion compensation configurations on phase noise with full compensation and check the reduction of phase noise along the fiber link.     

Optical all-pass filters for polarization mode dispersion compensation

Polarization mode dispersion (PMD) compensation is addressed by decomposition of a fiber's Jones matrix into amplitude and phase responses, which are then compensated for separately. Cubic and higher-order phase compensation substantially reduce the cumulative probability at a given system penalty over first-order PMD compensation, as demonstrated for a 40-Gbit/s non-return-to-zero signal and a fiber PMD with a differential group delay of 20 ps (rms). Single-stage all-pass filters provide tunable compensation that is comparable to that obtained with a variable-delay line, and multistage all-pass filters are well suited for higher-order phase compensation.